1. Field of the Invention
The present invention relates to an improvement of a mechanism for converting rotation of a driving shaft into reciprocation, in a reciprocating tool having a saw blade, file, or grinding tip attached to the distal end portion thereof.
2. Description of the Related Art
In a conventional reciprocating tool, a grinding/cutting tool, such as a saw blade, file, or grinding tip, is attached to the distal end portion of a tool holder. The tool holder is supported at the distal end portion of a grip section of a reciprocating mechanism for reciprocation. As a driving shaft of the reciprocating mechanism rotates, the tool holder is reciprocated. The reciprocating mechanism includes a bevel gear, which serves to reduce the speed of the rotation of the driving shaft and convert the rotation at right angles, and an eccentric roller mounted on a rotating shaft integral with the bevel gear. As the eccentric roller is fitted in a groove of the tool holder, the holder is reciprocated with a stroke corresponding to the eccentricity of the roller in eccentric rotation.
Conventionally, the eccentric roller is mounted on one end of the rotating shaft. In order to maintain the strength of the rotating shaft in some measure, the shaft must be supported by means of a plurality of bearings. If the eccentric roller is attached to the end of the rotating shaft, therefore, the shaft must be relatively long. Accordingly, the tool holder is reciprocated at a substantial distance from the axis of the driving shaft.
However, the tool holder, which projects in the form of a cantilever from the distal end portion of the grip section, is subjected to a force reactive to a force to press a grinding/cutting tool against a workpiece, and is bent corresponding to its length of projection. Also, such an undesired force acts not a little on the rotating shaft, which is fitted in the tool holder by means of the eccentric roller. If the tool holder is situated relatively distant from the axis of the driving shaft, therefore, vibration and power loss increase correspondingly, and there is a substantial difference in surface level between the grip section, containing a drive source, and the tool holder with the grinding/cutting tool therein. Thus, grinding/cutting operation is complicated and hard.